Better yet, just use the php5-uuid extension and this class to create 'official' UUIDs at high speed (On my system 1000 UUIDs are created in 0.0064 seconds) 

<?php 
echo "<br>";
echo "<br>";
echo "Usage: "; 
$uuid=new uuid(); 
echo $uuid->v1(); 

class uuid { 
    /** 
     * This class enables you to get real uuids using the OSSP library. 
     * Note you need php-uuid installed. 
     * On my system 1000 UUIDs are created in 0.0064 seconds. 
     * 
     * @author Marius Karthaus 
     * 
     */ 
    
    protected $uuidobject; 
    
    /** 
     * On long running deamons i've seen a lost resource. This checks the resource and creates it if needed. 
     * 
     */ 
    protected function create() { 
        if (! is_resource ( $this->uuidobject )) { 
            uuid_create ( &$this->uuidobject ); 
        } 
    } 
    
    /** 
     * Return a type 1 (MAC address and time based) uuid 
     * 
     * @return String 
     */ 
    public function v1() { 
        $this->create (); 
        uuid_make ( $this->uuidobject, UUID_MAKE_V1 ); 
        uuid_export ( $this->uuidobject, UUID_FMT_STR, &$uuidstring ); 
        return trim ( $uuidstring ); 
    } 
    
    /** 
     * Return a type 4 (random) uuid 
     * 
     * @return String 
     */ 
    public function v4() { 
        $this->create (); 
        uuid_make ( $this->uuidobject, UUID_MAKE_V4 ); 
        uuid_export ( $this->uuidobject, UUID_FMT_STR, &$uuidstring ); 
        return trim ( $uuidstring ); 
    } 
    
    /** 
     * Return a type 5 (SHA-1 hash) uuid 
     * 
     * @return String 
     */ 
    public function v5() { 
        $this->create (); 
        uuid_make ( $this->uuidobject, UUID_MAKE_V5 ); 
        uuid_export ( $this->uuidobject, UUID_FMT_STR, &$uuidstring ); 
        return trim ( $uuidstring ); 
    } 
} 
?>